While most, if not all, people in this country are fairly clear on what constitutes criminal behavior, many people would be hard-pressed to define what exactly constitutes a federal crime. A federal crime is any crime that is either committed on federal property, or violates a federal law.
Because of that, drug crimes, weapons crimes and even certain sex crimes can become federal crimes under the right circumstances. Most people would typically associate these types of crimes with the county or state criminal court system. Your defense attorney knows that there is a somewhat murky distinction between federal laws and regulations and those of individual states and even municipalities such as the city of Los Angeles.
The state of California can have laws regarding crimes and criminal behavior that are nearly identical to federal laws and regulations, in which case a crime can be investigated by either federal or local law enforcement agents. In some instances, local or state laws can actually be different from federal laws.
These points can actually create problems and pose a fundamental question about who should actually be in charge. Take, for instance, the matter of medical marijuana. Federal laws strictly prohibit the consumption of marijuana. Several states, including California, have made the use of marijuana legal under certain strict conditions in cases where it is medically useful. Technically, people with a valid prescription can use marijuana in California, though they can still be arrested by federal law enforcement agents.